Some people have claimed that they cannot yet sell IPv6 Internet access because there is no IPv6 firewall support. According to this ICANN study this is not quite true. At least 30% of the 42 vendors surveyed, had IPv6 support.

According to this talk many open-source and commercial firewalls supporting IPv6 are available.

ip6tables is used to build IPv6 firewalls in both openwrt and dd-wrt. Although dd-wrt and openwrt are built for wireless routers, you can turn off the wireless interface on these routers and use them as ethernet-to-ethernet routers.

DD-WRT supports IPv6 and runs on a lot of hardware, including the Linksys WRT 160N, IPv6 support is discussed here. (IPv6 firewall support not in the GUI, only from command line as of March 2011)

OpenWRT also supports IPv6 with both tunnelling and native, and also runs on a large amount of hardware, including both the Netgear WGR614L and Linksys WRT54GL. In the US, the WGR614L is stocked at www.amazon.com and the WRT54GL is stocked at Frys Electronics and is available at www.frys.com IPv6 support is discussed here.